This project will use cytochemical and electron microscopic methods to analyze mononuclear phagocyte development and function in normal and pathologic states. Chronic granulomata will be produced in the lungs of peritoneal cavities of experimental animals, and the endocytosis of various soluble and particulate tracers will be examined. Subsequently, the localization of lysosomal enzymes will be studied with the aim of elucidating the intracellular pathways involved in enzyme production and transport to pinosomes and phagosomes. The origin of alveolar macrophages will be studied by analyzing the cells which respond to an inflammatory stimulus in the lung. This investigation should resolve the question of how many monocytes emigrate from the blood into the lung, and how many mononuclear phagocytes emigrate from the interstitium of the lung into the alveoli in an inflammatory response. The development of monocytes in mice during treatment with the anti-inflammatory and immunosuppressive drugs, steroids and azathioprine, will be analyzed with the aim of distinguishing developmental differences which occur 1. when monocyte release into the circulation is inhibitied by steroids, and 2. when promonocyte division is suppressed by azathioprine. Extensive light microscopic cytochemistry will be used to analyze monocyte development in the bone marrow and blood of the pig. In this species, the two monocyte granule populations can be distinguished by their marked size differences which will aid in identification and subsequent cytochemical analyses of the granules. Lastly, the fate of peroxidase-positive and peroxidase-negative granules of monocytes will be investigated during phagocytosis.